The present invention is directed to a stage for moving an object. More specifically, the present invention is directed to a monolithic stage for an exposure apparatus.
Exposure apparatuses are commonly used to transfer images from a reticle onto a semiconductor wafer during semiconductor processing. A typical exposure apparatus includes an illumination source, a reticle stage retaining a reticle, a lens assembly and a wafer stage retaining a semiconductor wafer. The reticle stage and the wafer stage are supported above a ground with an apparatus frame. Typically, one or more motors precisely position the wafer stage and one or more motors precisely position the reticle stage. The size of the images transferred onto the wafer from the reticle is extremely small. Accordingly, the precise relative positioning of the wafer and the reticle is critical to the manufacturing of high density, semiconductor wafers.
A typical reticle stage includes a coarse stage and a fine stage. The coarse stage is used for relatively large movements of the reticle and the fine stage is used for relatively small, precise movements of the reticle. Existing reticle stages typically utilize a set of fine motors to move the fine stage and a set of coarse motors to move the coarse stage.
Unfortunately, existing reticle stages that utilize both a coarse stage and a fine stage have a relatively large total mass and are not very stiff. Further, the combination coarse stage and fine stage have a relatively low resonance frequency and a low servo bandwidth. As a result of the low resonant frequency and low servo bandwidth, external forces and/or small reaction forces can easily vibrate and distort the reticle stage. This will influence the position of the reticle stage and the performance of the exposure apparatus.
Additionally, the multiple sets of motors required for the coarse stage and the fine stage complicate the layout of the reticle stage and the system required to control the movement of the coarse stage and the fine stage. Moreover, these motors occupy valuable space near the stage, consume large amounts of electric current and generate a significant amount of heat. The heat is subsequently transferred to the surrounding environment, including the air surrounding the motors and the other components positioned near the motors. The heat changes the index of refraction of the surrounding air. This reduces the accuracy of any metrology system used to monitor the positions of the stages and degrades machine positioning accuracy.
In light of the above, it is an object of the present invention to provide a stage assembly having a stage with a relatively low mass, a relatively high resonance frequency and a relatively high servo bandwidth. Another object is to provide a stage assembly that is relatively simple to manufacture and control. Still another object is to provide a low mass stage that can simultaneously carry two reticles. Yet another object is to provide a stage assembly having a relatively stiff and compact stage. Another object is to provide an exposure apparatus capable of manufacturing high density, semiconductor wafers. Yet another object is to provide a stage assembly having a guideless stage.
The present invention is directed to a stage assembly for moving an object that satisfies these needs. The stage assembly includes a mounting frame and a stage frame. The stage frame includes a holder that retains the object. The stage frame is moveable along a X axis, along a Y axis that is substantially orthogonal to the X axis, and around a Z axis that is substantially orthogonal to the X axis and the Y axis. As provided herein, the stage assembly can be used to precisely position one or more objects during a manufacturing and/or an inspection process.
Uniquely, the stage frame is monolithic. The term monolithic as used herein shall mean and include systems with substantially a single moving part. With this design, the stage frame is relatively stiff and has a relatively high servo bandwidth. Because of the high stiffness and high servo bandwidth, external forces and small reaction forces are less likely to influence the position of the stage frame. This allows for more accurate positioning of the object by the stage and the production of higher quality wafers. Further, with this design, the stage frame is relatively easily to control.
As provided herein, the stage assembly includes a X mover that moves the stage frame along the X axis, and a Y mover that moves the stage frame along the Y axis. The X mover and/or the Y mover can also be used to move the stage frame about the Z axis. Additionally, the stage assembly can include a Z mover that moves the stage frame along the Z axis, about the X axis and about the Y axis. The X mover includes an X stage component, the Y mover includes a Y stage component, and the Z mover including a Z stage component.
The stage frame includes a first side section and a spaced apart, substantially parallel, second side section. The stage components of the X mover, the Y mover and the Z mover are secured to the side sections. As provided herein, the Y stage component and the Z stage component can be secured to the stage frame substantially directly above the X stage component. Additionally, the Y stage component and the Z stage component can be secured to the stage frame substantially directly below the X stage component. With this design, the forces from the movers can be directed through a center of gravity of the stage frame.
The stage frame provided herein is guideless with at least three degrees of freedom and more preferably six degrees of freedom. More specifically, the stage frame is not constrained along the Y axis, the X axis and about the Z axis and more preferably is also not constrained along the Z axis, about the Y axis and about the X axis. With this design, the movers can precisely control the position of the stage frame along the X axis, along the Y axis, along the Z axis, about the X axis, about the Y axis and about the Z axis. This allows for more accurate positioning of the stage frame and better performance of the stage assembly.
The present invention is also directed to a method for moving an object, a method for manufacturing a stage assembly, a method for manufacturing an exposure apparatus and a method for manufacturing a wafer and a device.